Lean / agile software development ideas are essentially modern management methods that take a sideways view at how things can be done. Mostly the ideas within the lean / agile body of knowledge are rooted in system theory and build on other work that has taken place in other sectors, particularly lean manufacturing. However lean manufacturing isn’t the same as lean software development because the type of work is different. While the underlying ideas are similar some of the tactics and emphasis has to be different.
Jon Terry presented an excellent talk on the lean / agile software development body of knowledge at our Agile Yorkshire event that can be an excellent foundation for further learning.